Don't put potatoes in your polytunnel if you plan to grow tomatoes in there next summer because of blight crossover problems.
Last year planted 80 cabbage plants in our tunnel, next morning rabbits had been in and eaten the lot
, this year it has been rabbit proofed with mesh so fingers crossed, we've got cabbages(red & white) calabrese, swedes & tunrips to go in over winter, even if they don't grow much over winter they give us a head start in spring as days get longer & hopefully warmer, just have to remember to water them from time to time and let some air thro.
HTH
mandy